Photographic antiplumming agents and emulsions containing them



United States Patent PHOTOGRAPHIC ANTIPLUMMINGAGENTS AND EMULSIONSCONTAINING THEM William B. Kendall, Rochester, N. Y., assignor toEastman Kodak Company, Rochester, N. Y., a corporation of New Jersey NoDrawing. Application May 3, 1954, Serial No. 427,373

3 Claims. (Cl. 957) This invention relates to improvements in theproduction of photographic images, such as images on paper supports,prepared from silver halide emulsions. More particularly this inventionrelates to silver halide emulsions having associated therewith a novelantiplumming or antibronzing compound which prevents image degradationof an exposed silver halide emulsion during processmg.

Silver halide emulsions after exposure often are subject to imagedegradation during processing, that is, during development, fixing,washing, toning, etc., and particularly When they encounter the moistheat to which they are subjected on drying as when prints are subjectedto ferrotyping or hot glazing. This degradation of the image frequentlymanifests itself as plumming or bronzing.

Heretofore, various compounds have been proposed for use with silverhalide emulsions to overcome such plumming and bronzing effects.

An object of the present invention is to provide a novel method ofproducing photographic images of superior quality. Another object is toprovide a method for preventing image degradation of an exposed silverhalide emulsion during processing. Still another object is to preventplumming or bronzing of photographic prints during a hot glazingprocess. Another object of the invention is to provide compoundssuitable for use as antiplumming agents in silver halide emulsions.Other objects will appear hereinafter.

In accordance with the present invention I have found thatendothiophenyl thiadiazoline thiol, and its potassium salt, areeffective antiplumming agents when employed with silver halidephotographic emulsions during processing of an exposed silver halideemulsion which term includes one or more of the operations ofdeveloping, fixing, washing and drying.

Potassium endothiophenyl thiadiazoline thiol may be prepared by themethod described in J. Prakt. Chem, 60, 206 (1899).

C H NHNH 20S KOH o 5 s 2 K S SE Potassium ethyl xanthate was prepared byadding 30 g. of carbon bisulfide to a solution of 16 g. of potassiumhydroxide in 50 m1. of ethanol. To the resulting slurry, a solution of20 g. of freshly-distilled phenylhydrazine in 60 ml. of ethanol wasadded gradually. The mixture at first thinned out, and then set upagain. It was heated with stirring, on the steam bath for four hours,then half of the solvent was distilled off, and the solution cooled inan ice bath. The white, crystalline potassium salt which separated wasremoved by filtration, washed with a little cold alcohol, and finallywith ether.

The free endothiphenylthiadiazolinethiol may be prepared by treating thepotassium salt thereof with hydrochloric acid.

In employing these compounds as anti-plumming or anti-bronzing agentseither one of them, or a suitable mixture thereof, may be addedpreferably to the emulsion layer or layers. They are also elfective ifadded to the developing solution, or to other layers carried on the Isensitive emulsion support such as the backing layer or supercoat.Alternately the sensitive layer may be bathed in a solution of theagentafter exposure but prior to development. amounts between 0.1 and 4.0grams per, molof silver halide in the emulsion. I

These two compounds are very effective an anti-plumming agents whenemployed in any of the ways herein described including bathing thedeveloped image in a solution of the compound after fixation. Asuitablebath for example in an aqueous solution containing 0.5 to 2.0 .1

grams per liter of the compounds.

amples Example 1 An emulsion was prepared in accordance with Examples lof U. S. Patent 2,596,756. To separate portions .of this emulsion wereadded quantities of a 1:500 aqueous solution of potassium endothiophenylthiadiazoline thiol equivalent to 0, 0.5, 1.0 .and 2.0 grams per mol ofsilver.

These separate portions were then coated on separate sheets of glossybaryta coated single weight paper at a rate of 700 sq. ft. per mol ofsilver. Two samples of each coating were exposed through a step wedge,developed, fixed and washed. One set of prints was dried without heatand the other set was dried on a ferrotype drum at to 200 F. Thereflection D-max values obtained are tabulated below:

Dried Dried fg with heat A second series of experiments was performed inthe same manner as the first except that different levels of potassiumendothiophenylthiadiazoline thiol were used. The reflection D-max valuesobtained are tabulated below:

be as strong an antiplumming agent as the potassium salt, as thefollowing will illustrate.

An emulsion was prepared according to Example 1 of U. S. Patent2,596,756. To portions of this emulsion were added quantities of a 1:200solution of endothiophenylthiadiazoline thiol dissolved in equal partsof methanol and acetone, and equivalent to 0, 0.5 and 2.0 g./mol ofsilver. These emulsions were then coated on glossy baryta-coatedsingle-weight paper at a rate of 650 ft. mol of silver. Two samples ofeach coating were exposed through a step wedge, developed, fixed andwashed. One set of prints was dried without heat, and the other PatentedApr.

These agents are employed preferably in 1 My invention is furtherillustrated in the following 'ex- 3 sets/as dried on a ferrotypedru'm at180-200" F. The reflection D-max values obtained are tabulated below:

1 3 21 D a I'le 1'18 Without With Heat.

Heat

While inthis specification I have described my invention mainly 'withreference to the use of these anti-plumming agents in developingsolutions and anti-plumming baths, my invention is not limited to suchtreatments.

adsorbed to the silver grains to give the desired anti-plumming effectduring hotglazing of the print.

I claim:

1. The method'of preventing'image degradation of an exposed silverhalide emulsion during drying which comprises performing at least one ofthe steps of developing,

. 4 fixing, washing and drying said emulsion in the presence of acompound having the formula:

2. A photographic silver halide emulsion containing from 0.1 and 4.0grams per mol of silver halide of a compound having the formula:

oeH51 -N K- -s11 s 3. A photographic element containing a silver halideemulsion and from 0.2 and 7.0 milligrams per square foot of a compoundhaving the formula:

References Cited in the file of this patent UNITED STATES PATENTS2,353,754 Peterson July 18, 1944 FOREIGN PATENTS 471,339 Canada Feb. 6,1951

1. THE METHOD OF PREVENTING IMAGE DEGRADATION OF AN EXPOSED SILVERHALIDE EMULSION DURING DRYING WHICH COMPRISES PERFORMING AT LEAST ONE OFTHE STEPS OF DEVELOPING, FIXING, WASHING AND DRYING SAID EMULSION IN THEPRESENCE OF A COMPOUND HAVING THE FORMULA: